Tapered optical fiber for coupling to diffused optical waveguides

Abstract

An optical fiber having an a core with a D-shape or an oval shape at an endface. The optical fiber tapers from a round, cylindrical section to the endface so that adiabatic mode transformation is provided. Preferably, the D-shape or oval shape is selected so that the optical fiber has a mode shape at its endface that matches the mode shape of a diffused waveguide.

1. An optical for coupling to a waveguide, comprising:
 an optical core comprising a large-width section of a first width and a small-width end section of relatively smaller width;  
 a core taper section extending between the large-width core section and the small-width core end section, the taper dimensioned to provide a gradual transition between the large-width and small-width core sections to permit adiabatic mode transformation between the large-width and small-width core sections, wherein the taper section includes a sidewall inclined at an angle in the range of 0.01 to 5 degrees relative to the fiber axis; and  
 
       a core endface at the small-width core section, the core endface having a non-circular cross-sectional shape in a plane perpendicular to the core axis. 
     
     
       2. The optical fiber of  claim 1  wherein the taper section includes a sidewall inclined at an angle in the range of 0.1 to 2 degrees relative to the fiber axis. 
     
     
       3. An optical fiber for coupling to a waveguide, comprising:
 an optical core comprising a large-width section of a first width and a small-width end section of relatively smaller width;  
 a core taper section extending between the large-width core section and the small-width core end section, the taper dimensioned to provide a gradual transition between the large-width and small-width core sections to permit adiabatic mode transformation between the large-width and small-width core sections, wherein the taper section extends over a length in the range of 100-10000 microns; and  
 a core endface at the small-width core section, the core endface having a non-circular cross-sectional shape in a plane perpendicular to the core axis.  
 
     
     
       4. The optical fiber of  claim 3  wherein the taper section extends over a length in the range of 300-3000 microns. 
     
     
       5. The optical fiber of  claim 3 , wherein the taper section comprises a compressed core segment. 
     
     
       6. The optical fiber of  claim 3 , wherein the taper section comprises a polished core segment. 
     
     
       7. The optical fiber of  claim 3 , wherein the core endface comprises a non-rectangular cross-sectional shape. 
     
     
       8. The optical fiber of  claim 7 , wherein the core endface comprises an oval cross-sectional shape in a plane perpendicular to the core axis. 
     
     
       9. An optical waveguide device comprising:
 an optical fiber comprising: 
 an optical core comprising a large-width section of a first width and a small-width end section of relatively smaller width;  
 a core taper section extending between the large-width core section and the small-width core end section, the taper dimensioned to provide a gradual transition between the large-width and small-width core sections to permit adiabatic mode transformation between the large-width and small-width core sections, wherein the taper section extends over a length in the range of 100-10000 microns; and  
 a core endface at the small-width core section, the core endface having a non-circular cross-sectional shape in a plane perpendicular to the core axis; and  
 
 a diffused optical waveguide optically coupled to the optical fiber at the fiber core endface.  
 
     
     
       10. An optical waveguide device comprising:
 an optical fiber comprising: 
 an optical core comprising a large-width section of a first width and a small-width end section of relatively smaller width;  
 a core taper section extending between the large-width core section and the small-width core end section, the taper dimensioned to provide a gradual transition between the large-width and small-width core sections to permit adiabatic mode transformation between the large-width and small-width core sections, wherein the taper section includes a sidewall inclined at an angle in the range of 0.01 to 5 degrees relative to the fiber axis; and  
 a core endface at the small-width core section, the core endface having a non-circular cross-sectional shape in a plane perpendicular to the core axis; and  
 
 a diffused optical waveguide optically coupled to the optical fiber at the fiber core endface.  
 
     
     
       11. The optical fiber of  claim 10 , wherein the taper section includes a sidewall inclined at an angle in the range of 0.1 to 2 degrees relative to the fiber axis. 
     
     
       12. The optical waveguide device of  claim 9  wherein the taper section extends over a length in the range of 300-3000 microns. 
     
     
       13. The optical waveguide device of  claim 9 , wherein the taper section comprises a compressed core segment. 
     
     
       14. The optical waveguide device of  claim 9 , wherein the taper section comprises a polished core segment. 
     
     
       15. The optical waveguide device of  claim 9 , wherein the core endface comprises a non-rectangular cross-sectional shape. 
     
     
       16. The optical waveguide device of  claim 15 , wherein the core endface comprises a D-shaped cross-sectional shape in a plane perpendicular to the core axis. 
     
     
       17. The optical waveguide device of  claim 15 , wherein the core endface comprises an oval cross-sectional shape in a plane perpendicular to the core axis. 
     
     
       18. The optical fiber of  claim 7 , wherein the core endface comprises a D-shaped cross-sectional shape in a plane perpendicular to the core axis.